Percentage Calculator
Calculate percentages, proportions, and percentage change with a clear formula breakdown.
How do I calculate a percentage?
A percentage of a number is the number multiplied by the percentage and divided by one hundred; to go the other way, divide the part by the whole and multiply by one hundred.
Formula: A percentage is a share of 100. X% of Y = X ÷ 100 × Y. X as a percentage of Y = X ÷ Y × 100, where Y cannot be zero. Percentage change = (new value − original value) ÷ |original value| × 100, where the original value cannot be zero; the sign shows increase or decrease.
What this calculator does
Choose a percentage question, enter two values, and get an instant result with the calculation steps.
Use it to turn What do you want to work out?, First value, Second value into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this math calculation.
Inputs and what they mean
- What do you want to work out?
- — choice value.
- First value
- — number value.
- Second value
- — number value.
How to use it
- Choose the percentage question you want to answer.
- Enter both values using whole numbers or decimals.
- Read the result and calculation breakdown.
Formula
Use X% of Y when you know the rate and the base value, such as 25% of 200.
Use X is what percent of Y when you know the part and the total; the total must be non-zero because division by zero has no finite answer.
Use percent change when comparing an old value with a new value. The calculator divides by the absolute original value so a negative starting value still gives a signed change direction.
Results are rounded for display only; the calculation itself uses the numeric values you enter.
A percentage is a share of 100. X% of Y = X ÷ 100 × Y. X as a percentage of Y = X ÷ Y × 100, where Y cannot be zero. Percentage change = (new value − original value) ÷ |original value| × 100, where the original value cannot be zero; the sign shows increase or decrease.
Inputs used: What do you want to work out?, First value, Second value.
Worked example
Find 25% of 200
- Start with the percentage, 25, and the base value, 200.
- Convert the percentage to a decimal: 25 ÷ 100 = 0.25.
- Multiply by the base value: 0.25 × 200 = 50.
- The answer is 50; the remaining amount is 200 − 50 = 150.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- The calculator treats percentages as pure arithmetic; it does not decide whether a tax, fee, discount, or interest rate legally applies.
- Modes that divide by a total or original value reject zero because no finite percentage can be calculated.
- Displayed answers are rounded, so use the breakdown to understand the calculation rather than treating every displayed decimal as exact.
- The result depends on the values you enter for this percentage calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
How do I calculate a percentage?
A percentage of a number is the number multiplied by the percentage and divided by one hundred; to go the other way, divide the part by the whole and multiply by one hundred. Check the formula, example, and limitations on this page before using the result for a real math decision.
How do I calculate a percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100. For example, a move from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. Choose the percent-change mode above when you want the calculator to keep the increase or decrease direction clear.
What is the difference between percentage of and percentage change?
Percentage of finds a portion of one number, such as 15% of 80. Percentage change compares two values and measures the difference relative to the original value. The two formulas answer different questions, so choose the mode that matches the wording of your problem.
Why can the total or original value not be zero in some modes?
The 'X is what percent of Y' and percent-change modes both divide by the comparison value. If that value is zero, the result is not a finite percentage. The calculator rejects that case instead of showing an invalid or misleading number.
Can I use decimals or negative numbers?
Yes, decimals are supported in all modes. Negative numbers can be used when the formula has a finite meaning, and percent change keeps the sign of the difference so you can see whether the result is an increase or decrease.
How do I use the Percentage Calculator?
Enter the required values for What do you want to work out?, First value, Second value. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
Cite this page
Free Calculator. (n.d.). Percentage Calculator. https://freecalculator.tech/tools/percentage-calculator
"Percentage Calculator." Free Calculator, https://freecalculator.tech/tools/percentage-calculator.
Percentage Calculator — Free Calculator, https://freecalculator.tech/tools/percentage-calculator
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